What's a Motorsailer?
Experts' opinions on motorsailers & motorsailing (Click to go)

"I sincerely believe that a well conceived Motor/Sailer is the most practical, capable, comfortable, economical vessel for serious ocean passagemaking......and retaining the ability to explore the most remote coastal areas."  Brian Eiland

All contributions on motorsailers matters are most welcome.
Write to: g.gefaell<at>mundo-r.com    (Substitute <at> with @ )



What's a motorsailer?
 by Guillermo Gefaell.

Many has been written and discussed about what can be understood as a motorsailer nowadays. You can find several opinions and thoughts about motorsailers and motorsailing, downwards in this page, from a variety of experts. Today the motorsailer concept seems to have widened from that of a fishing boat with small steading sails, to ultimate fast expedition catamarans, or even trimarans, as some builders understand the concept nowadays. On the other hand, slipping through the range of the ubiquitous relation of sailing ability vs. powering ability  , we find lots of imprecise talking about 30-70, 50-50 and even down to 20-80 combinations.

Some authors and boatyards include today into the motorsailer philosophy pure sailing boats (even light displacement ones), just because of the addition of a low profile pilothouse and a powerful engine. On the contrary,  there are some fishing boats transformed to recreational, with a couple of steadying sails, also heartly classified as motorsailers by their owners.


If you navigate through the enormous amount of web pages where sailing boats are for sale or hire, you'll find yourself confusingly struggling with the question of what on earth a motorsailer is, as so many different boats are offered under this description, with a particular accent in the charter world, where almost everything, but the obvious, is called a motorsailer.

From the point of view of Francis Kinney's motorsailers definition you'll find downwards in this page, almost all sailing boats with an engine under production nowadays could be classified as motorsailers: Engine powering and running a boat today is proportionally much cheaper than it was 50 years ago; and with the new breed of small sized and powerful diesel engines, added to the general boaters appetency for  fast passages, it makes no sense for the sailing boat builder/designer to specify propulsion systems not able to bring the boat well up to its hull speed (more or less 1.34 Froude's number); unless we are talking about competition machines, where saving even grammes is important, of course!

So, to avoid misunderstandings, I think we should always refer to some simple parameters that easily tell us if a certain boat may be considered a motorsailer or not. Actually there are some well known ones of easy and universal use, that more or less define motorsailers. One of them is the  Displacement / Waterline length ratio, D/Lwl. Motorsailers use to move in the 300+ zone for this parameter.  The above mentioned Sailing / Powering ability ratio, varying from 20/80 to 50/50, also give us a clue, but it is quite imprecise because is more based on wishful thinking than in empirical data. The Sail area / Displacement ratio, SA/D, with motorsailers being under 14, is also an useful and simple parameter.  

But some times Displacement is a not a well known factor (many times just guessed) and parameters using this factor are not easily workable without a calculator, while Sail area and Waterline length are simple and straightforward data, able to be easily measured with enough accuracy by non specialized people. So I think we should have formulae based in these two data, easy and simple to be obtained by most owners and aficionados. Shall we be able to find such formulae? We'll try downwards in this paper.

Now, as motoring is an essential motorsailer's characteristic, we should define what amount of engine power should be considered the minimum for a proper motorsailer, as well as what should be the minimum sail area allowing for enough sailing ability for a safe sailing under sails alone (Of course assuming some kind of hull and rig efficiency!).

I have analized Banjers' parameters with several sail area plans, and I have come to the already known conclusion that, to get what is known as a 50/50 motorsailer, you should go up for an SA/D ratio of 14.  A ratio of 9 would do for a 40/60 motorsailer (40% sail, 60% power) and,  from my point of view, SA/D ratio should never be less than 8 for a minimally effective sailing rig, which is something like 37/63 and what seems to be the lower limit for a "secure" sail area, that is, having enough sail power to claw off a lee shore under sail alone as Kinney states. Let's say, then, that with a SA/D under 8, what we have are motor boats with auxiliary or steadying sails, not effective motorsailers.  This coincides with Skene's book stated formula which says that to have a motorsailer you need at least as many sail area as the squared Lwl divided by two.

On the upper side, we shouldn't have lots of sail area, because I think motorsailers have to be effective enough under sail alone, for sure, but sails have also to be easily manegeable and center of effort has to be kept as low as possible, so the induced heel is comparatively low. Low aspect ketch rigs are probably the most adecuate to this end, and even the use of gaffs may have to be considered as a bonus. Maybe these kind of rigs are not highly efficient going to winward, absolutely, but we are talking about motorsailers: We should almost always motorsail when beating hard to winward and, on the other hand, we'll have a comfortable rig to manage strong winds as well as an efficient one when running in a tradewind.  

And, in addition to these considerations, we should not forget that one of the important characteristics of motorsailers is having a high loading capacity without losing too much performance, as well as enough internal volumes to allow for comfortable accomodation for long periods of time. All this doesn't call for highly effient underbodies for when under sail alone, so it makes no sense to go for big amounts of sail area, nor high aspect ratio rigs. Either it doesn't call for a catamaran concept, in my humble opinion, although I know many disagree. And catas or tris have the extra penalty of much higher marina fees in most places.

I think that with SA/D ratio being over 16, what we get are different types of sailing boats, from heavy oceanic cruisers up to modern racing machines, not motorsailers. Boundaries are not strict, of course, and most times categories of heavy oceanic cruisers and motorsailers overlap one with the other, and it's difficult to say which is what.

Banjers Main Data
LOA :      36.52'
Lwl:        31.17'
Beam:   11.42'
Bwl :        9.84'
Draft:       4.43'
Displacement: 27778 pounds
Sail Area : 301, 450 & 807 sq feet
                     (28, 42 & 75 sqm)
Power: 61 or 95 BHP (DIN)
D/Lwl:     409.5
HSPD:    7.48 kn
SA/D:      5.25, 7.88, 14.08
Lwl/B:     2.73
MCR:      61.57
CSF:       1.31

D/Lwl : Displacement / Waterline length  
Displacement to LWL: A medium value would be 200. 300 would be high (Heavy Cruising Boat) and 100 would be low (Ultra Light Displacement-ULDB). Boats with low numbers are probably uncomfortable and difficult to sail.

HSPD: Hull speed
Hull Speed: This is the maximum speed of a displacement hull. Somewhat tricky, as Lwl is not static an varies with speed and heeling. It is possible to surpass the HSPD even for "heavy wheights". For instance, Banjer's HSPD has been found in real life tests to be as high as 8.5 knots, while theoretically is 7.5. Some racers and lighter boats are able to achieve even greater speed by lifting over the bow wave and riding on top of the water, that is, planing. Slender catamaran hulls are able also of easily surpassing theoretical HSPD.

SA/D:  Sail area / Displacement
Sail Area to Displacement: The sail area is the total of the main sail and the area of the front triangle. A racing boat typically  has large sail area and low displacement. A number less than 13 most probably indicates that the boat is a motorsailer or a motor boat with auxiliary sails. High performance boats would be around 18 or higher.

Lwl / B : Waterline length / Beam
LWL to Beam: A medium value would be 2.7 ;  3.0 would be high and 2.3 would be low

MCR:  Motion Comfort Ratio
Motion Comfort: Range will be from 5 to 60+ with a Whitby 42 at the mid 30's. The higher the number the more comfort in a sea. This figure of merit was developed by the Yacht designer Ted Brewer and is meant to compare the motion comfort of boats of similar size and types.

CSF: Capsize ratio
Capsize Ratio: A value less than 2 is considered to be relatively good; the boat should be relatively safe in bad conditions. The higher the number above 2 the more vulnerable the boat. This is just a rough figure of merit and controversial as to its use.

To better understand some of the parameters and ratios up here, you may go toTed Brewer's Understanding Yacht Design, or  Dan Pfeiffer's  Sail Boat Design Ratios

My own Banjer  "Marie", with an SA/D ratio under 8
I consider her as a motor boat with auxiliary sails.
Her actual rig is pretty nice when in strong winds, but she hardly moves in someting less than a force 4.
As I do not want higher masts, because of some bridges at my home waters,
I'm considering about a gaff rig, or even about mounting an square sail in the main mast,
as I've seen in some Ray Benford's designs, to allow for higher efficiency when running.

On the engine's power side, we need enough power to easily attain hull speed, as said before, but I should say even having enough reserve of power to beat to windward in strong gale conditions.  For Banjers like motorsailers, I think we should have a rated BHP (DIN) of no less than 1.85 * Lwl (feet), or 6.07 * Lwl (metres)  to achieve this, assuming the prismatic coefficient is adecuate to allow for efficient forms at hull speed, something like 0.63, as well as mounting an efficient 3 blades propeller turning at an r.p.m. number as slow as practical (With most actual medium speed diesel engines, this calls for a 3:1 gear ratio).

I think also that, for Banjers like boats, it is not necessary at all to go for an engine's power higher than 2 * Lwl (feet). Using the 1.85 factor equation provides, to my experience, power more than enough to beat to winward in strong gale conditions and, definitively, going higher than 2 means unnecessarily overpowering the boat and probably a nice way of expending money. So I'll tighten to the 1.85 factor for the time being.

And last but not least, appearance: From my point of view, the overall design of the boat should bring us an air of traditional reminiscences, bred on local working boats, the origin of the class. To this end, motorsailers should be, in my humble opinion, single hulled, with lines more or less derived from working boats (so long keelers), and have a proper, enclosed and protruding pilothouse, which's main use should be to steer and navigate, not to be a deck saloon. But let's not make of this last point a controversial item, because there are some beautiful examples of real motorsailers around there with no pilothouses, as my friend Dees' beautiful "Kittyhawk". So we'll talk about Motorsailers, in general, and Pilothouse Motorsailers as a class on its own.

Kittyhawk

Now, avoiding the pilothouse issue and aesthetical considerations, let's try to arrive to simple formulae based on SA and Lwl for "classic" motorsailers, as we told before. Is that possible? We'll try. Let's go to it:

First of all it has to be clear that we will work only with munohulled long-keeled boats, conceived to be fuel-efficient under the power of an optimized propeller. Under these limitations, we may define Classic Motorsailers (as a first approach), as boats complying with the following:


Classic Motorsailers formulae
BHP(DIN) > F * Lwl
8 < SA/D < 14
  (Imperial units)

Notes:

1.- "F" would be a factor given in a table for different ranges of length, as power varies non linearily with Lwl. And also, as for a given Lwl power needed for a given speed varies linearily with displacement, we'll have an eye on this.

We'll try to find how this "F" factor varies for different lengths with the help of readers. I'll be grateful to people sending me their motorsailer's (Or one known to them) main data, by fulfilling the form downwards in this page.

2.- Second equation is more or less the same than saying that a motorsailer should have a sail/power ratio within the 37/63 to 50/50 range. Boats with a 35/65 ratio or less should be definitively defined as motorboats with auxiliary or steadying sails, not proper motorsailers.


TABLES OF MOTORSAILERS' DATA

Let's now work data from several motorsailers we got navigating Internet and also with the help of some friends:

Motorsailers data:
Model
Fisher 25
(Ketch)
Dartsailer 27
Claymore 30
(Sloop)
Cape Dory 30 MS
Fisher 34
(Ketch)
Banjer 37
(75 sqm)
Fisher 37
(Ketch)
Lwl (ft)
21.00
22.97
24
26.51
29.83
31.17
32.5
D (lb)
10080
11032
14112
11500
25780
27800
31360
D/Lwl
486
406
456
276
433
410
408
SA (sqft)
290
335
405
477
626
807
844
SA/D
9.94
10.81
11.1
14.98
11.48
14.07
13.58
BHP (DIN)
22 - 27
41
36
?
61
61
82
K
1.05 - 1.29
1.79
1.5
?
2.06
1.96
2.52
Notes:
The Fisher 25 is really a heavy-weight. 22 HP seem to be good enough to move her even against strong winds, as per Dave Herndon feedback,  but  newer units come now with a 27 HP engine.
The Dartsailer seems to be quite overpowered.
Cape Dories are quite beamy and light.  
Actual "aged displacement" for Banjers seems to be more in the vicinity of 31000 lbs, so D/L is around 455 and SA/D around 13.8
Banjers are considered with Perkins 4236 engine. Banjers with Perkins 6354 (95 BHP cont.) are quite overpowered.
Fisher 37 seems to be also overpowered.


More data...
Model
Panoceanic 38
Northeast
400
Panoceanic 43
Perry 43 MS
(Ketch)
Alaska 43
Gartside 45
Panoceanic 46
Lwl (ft)
31.13
34
36.33
36
38
38.5
36.5
D (lb)
18750
21900
27500
34000
35000
35380
33500
D/Lwl
255
249
256
325
285
277
307
SA (sqft)
719
686
970
832
1048
937
1093
SA/D
16.3
14.02
17.03
12.62
15.67
13.91
16.83
BHP (DIN)
?
82
?
67
70
80
?
K
?
2.41
?
1.86
1.84
2.08
?
Notes:
Panoceanics are better classified as fast oceanic cruisers, rather than motorsailers. Anybody knows engines powers?
Northeast 400 seems also to be quite overpowered. She performs an interesting AeroRig.
I'd say there are two different schools for monohull motorsailers design: Northern and Southern. Northerns are usually heavywheights (D/L>400), bred on displacement fishing boats lines and, on the contrary,  Southerns tend to be lighter (250-350), being rather bred on sailing boats lines.



CONCLUSIONS (Tentative)

1.- Analizing the upper data, and eliminating some extreme values, we find, as first approach that, for our concept of a proper "classic" motorsailer and always talking of DIN BHP, engine's rated power should be in the range of:

HP = 5 * Displ. (tons or tonnes)  
(or 2.23 HP per 1000 lbs)
Formula 1
Many boats go higher nowadays, certainly, but I think it's really not necessary, unless there are a lot of appliances aboard needing a huge extra energy, or you want to go into semi-displacement or planning mode, which is far away from motorsailers concept, in my opinion. This formula uses Displacement, so it's applicable to all monhulled moitorsailers, be them heavy or light ones.


2.- If we do not know displacement, but suspect the boat we are considering is a heavy weight motorsailer (D/L over 400), we may measure Lwl and, although things are more tricky here, use the following approximate formula for Lwl between 20 and 40 feet:

HP = 0.1 * Lwl * (Lwl - 10)
Formula 2

3.- Also taking in account the analized data and making things easier to remember, we can refine the previous SA/D factor criteria and say that, for an efficient motorsailer, values should be between:

13 < SA/D < 15
Formula 3

This ratio may go to as low as 10. I maintain the criteria that boats with an SA/D ratio under 8 should not be called motorsailers, absolutely, but motor-sail assisted-boats . Let's keep a twilight zone from 8 to 10...

NOTES:
- These formulae are still precarious and I have to do more extensive search. So take them with care.
- You will not make big mistake, if you use indifferently tonnes (2204 lbs) or tons (2240 lbs).
- You will not make big mistake, either, if you take Hull Length instead of Lwl in formula 2, and multiply obtained figure times 0.86 to get HP, for classic style motorsailers with normal overhangs.
- DIN and SAE standards power measurements are not equal. SAE gives power without engine's accesories and has a greater value (Nice for sales purposes!). To convert from DIN to SAE, you may (roughly!) multiply times 1.13, as a mean value.
- To know more about differences between BHP, SHP, EHP and the like, visit this educational page of the USNA (click).


GENERALIZATION OF FORMULA 2
We may generalize Formula 2, to easily estimate HP (DIN) for monohull motorsailers when displacement is not known, as the following:

General HP / Lwl formula:
HP = K * Lwl * (Lwl - 10)
for 20 < Lwl (feet) < 40  

being K values:
Motorsailer type
Light
Medium
Heavy
K
0.06
0.08
0.1
D/Lwl ratio's zone:
250
350
450

If we know D/Lwl ratio, we may use:
K = (D/L)/4300

But if we know D, its easier to use a generalization of the formula in Conclusion 1 above:

Formula 4
imperial
 HP = µ * D(lbs)/1000
being µ among 2 and 2.5

or, in metric units (and very approximate the same in long tons)
 HP = µ * D(tonnes)
being µ among 4.5 and 5.5


Sailing boats with power given by this last formula with a  µ  less than 1.5 (imperial) or 3.3 (metric), can be considered as sailing boats with auxiliary engines. On the other hand I think it's not necessary at all to go over 3 (imperial) or 6.6 (metric) for this parameter unless for semi-planning hulls.



FORMULA 2 IN TERMS OF SA AND Lwl
It is no easy to come to a simple formula expressing SA in terms of Lwl. I've been trying hard, but it comes to a too complicated one, because it depends too much on others factors. Anyhow, simplifying things, we can consider that a proper motorsailer should have a sail area in square meters (or 10 times if in sqf), in the range of what I consider a proper engine's power in HP (HP/D ratio between 2 and 2.5). If we asume this, we may also use the same Formula 2 generalized, to estimate the Sail Area given the Lwl.

So, we can finally state the following:


HP &  SA  estimative formula (Imperial units):
HP = SA/10 = K * Lwl * (Lwl - 10)

for Lwl between 20 and 40 feet  ,  being K as before



MOTORSAILERS' DEFINITIONS (MONOHULLS)

Here you have my actual thoughts and definitions on Motorsailers.

General definition:
"Motorsailers should be, in my opinion, hybrids among sailing boats and motor boats, having amplier volumes than those of a pure sailing boat, as well as a nice pilothouse conceived to steer and navigate (so not being being only a deck or raised saloon) to make them more livable in all kind of weathers; able to carry a generous cargo; have manegeable sails with a short crew (without the needing of very expensive hardware), but able to easily pull the boat as to develope hull speed under sail alone in a moderate breeze (force 4); have a propeller-engine combination allowing for a fuel efficient motoring and having power enough to at least reach hull speed under engine alone, as well as extra muscle to beat dead to winward in a Force 10 storm in protected waters".

We have two main classes, depending on the intended use:

Ocean going (globetrotters) motorsailers:
They use to have an SA/D ratio (loaded) from 13 to 15+ and a HP/(D/1000) ratio around 2 (from now on we'll call this ratio just HP/D). D/Lwl ratio may go from 250 for lighter ones as in designs bred in sailing boats, up to 400+ for old-style heavy-weigths, bred in fishing boats. Fuel tankage should be enough, at least, for around 900-1000 miles under engine alone at 1.1  Speed/Length ratio (Imperial units). Low pilothouse profile, as to allow for structure and windows being capable of resist capsizing and green sea slamming. Relatively high wetted surface for better seamanship. CE Design Category: A

Coastal motorsailers:
These tend to be lighter nowadays and with more powerful engines, although traditional heavy-weights are also here in their own. Fuel tankage is shorter, tipically allowing for 300-400 miles passages. CE Design Category: B or A  
Two definite trends:

Northern: Boats designed to usually sail in colder climates and stronger weather. D/Lwl ratio going from 250 to 350 (oldies use to be in the 400+ region), SA/D  from 13 to 16 and,and HP/D ratio from 2 to 3 (I consider these boats as being all around short-seas motorsailers, if design category is A).

Southern: Boats rather designed with good-weather islands hopping in mind. D/Lwl in the 200-250 range, very variable SA/D ratio, going from 12-13 up to the 17-18 range, and having an HP/D ratio definitively much higher than 3, some of them going as high as 7 (!) with totally flat sections at the sterns. Fuel hungry boats. Raised deck-saloons rather than pilothouses, in some cases integrated with the cockpit (Be careful: Extreme designs may not even comply with CE design category B!)

Note: Ratios always considered for loaded condition

All contributions on these matters are most welcome and appreciated.

Write to: g.gefaell<at>mundo-r.com    (Substitute <at> with @ )



 SEND YOUR MOTORSAILER DATA!
You may send your (Or known to you) motorsailer's data using the form down here.
Please send also images. Thanks a lot in advance!

GATHERING INFO ON MOTORSAILERS
Please use metric units if possible
(but you may use imperial too)

Sailboat Data Form


A JPG photo of your boat sent by e-mail, as well as an stability curve, if available, will be greatly appreciated.

Please add your comments on the seakindliness, seakeeping ability and seaworthiness of your boat.

Also the kind of cruising you consider your boat is better suited to: oceanic, offshore, inshore, protected waters, etc.

You may also send me whatever additional information to:

g.gefaell<at>mundo-r<dot>com
(Substitute <at> with @ and <dot> with "." )


THANKS A LOT!






You may use this Triangle calculator,
to easily calculate your boat's sail area:

(Clik on image to access)

Note: Forward triangle foot is not your jib's foot but the "J" measurement. As an approximation you may measure your working jib (Not the Genoa)


If you need a handy calculator
to figure out your boat's numbers,
here you have an useful one!

Note:
Enter angles in radians.
1 radian = 180º/Pi = 57.25978º (aprox)
1º = 0.0174533 radians (aprox.)

(For a converter, try: Megaconverter)





 EXPERTS OPINIONS ON MOTORSAILERS & MOTORSAILING


Motorsailers?
by Larry Zeitlin
Click on the link to find precise, well founded and comprehensive opinions from Larry, at Trawler World Forum.
Here you have some excerpts:

It is hard to be precise about the characteristics of a motorsailer. Francis Kinney, who revised "Skene's Elements of Yacht Design", gives a general insurance company rule that says a motorsailer is a yacht with enough engine power to achieve hull speed AND enough sail power to claw off a lee shore if the power fails. He states that insurance companies conclude that this requires at least a sail area equal to the LWL squared, divided by two. Thus an adequately powered sailboat with a 40 ft. LWL should, for insurance purposes, have at least 800 sq. ft. of sail area to be classed a motorsailer. Less than that and it is basically a powerboat with steadying sails. Juan Baader, in "The Sailing Yacht" has a much more pragmatic rule. He says that if a yacht is faster under sail than under power it is an auxiliary powered sailboat. On the other hand, if it is faster under power than under sail, it is a motorsailer.

The balance between sailing and powerboat characteristics is often expressed by a ratio. A 70/30 ratio would imply that the boat is a better sailboat than a powerboat while a 50/50 ratio indicates that the abilities are about equal. Passagemaker would best be described as a 20/80 boat, i.e. a much better trawler than sailboat. Beebe complained that the sails were too small to offer much in the way of propulsion or roll damping. My own Willard Horizon, the W30 hull with a sailing rig, is a 30/70 boat. It can make reasonable headway under sails but compared to a real sailboat, the performance is marginal. For larger auxiliary cruising sailboats the point is moot since most are equipped with engines of sufficient power to propel them at hull speed. More important is the type of propeller. Efficient trawler type propellers have enough drag to slow a boat appreciably when under sail. When motorsailing, using both wind and engine power, the prop turns relatively slowly and should have a large pitch. Under power alone, say when punching into wind and seas, the pitch should be small enough to let the engine achieve full power. The only feasible prop that will perform well in both regimes is a CPP, an expensive but practical solution. Nordhavn has chosen to use a Hundstrand CPP which can be full feathered under sail. Good for them. Price, on Nordhavns, is rarely an object of concern. All current motorsailers feature a pilothouse with full headroom and an internal helm. In fact this feature almost defines the class. Several manufacturers, including Pacific Seacraft, build boats with identical hulls and differing deck moldings. Those with a pilot house are called motorsailers, those without are called auxiliary powered sailboats. The type is much more popular in Northern Europe where typical boating conditions are such that most American yachtsmen would be heading for the nearest bar in search of a hot toddy. As the population of sailors ages, it is likely that the proportion of motorsailers will increase. To quote Baader, "A well balanced motorsailer combines excellent seaworthiness with good sailing qualities. Older yachtsman tend to turn toward motorsailers, since, although they have not lost their enthusiasm for sailing, they are more exacting with regard to comfort below decks and like to have more auxiliary power which makes them independent of the sails for difficult maneuvers or in bad weather."

A 30/70 motorsailer, like mine or any of the Fisher class, uses its engine most of the time although it can make reasonable progress under sail if the wind is favorable. Most boats of this type have beamy hulls, full length ballasted keels and drag a big three bladed fixed pitch prop, features not conducive to sailing efficiency. On the whole, the sailing performance of the class would be roughly equivalent to one of Columbus's caravels or perhaps a 19th century workboat, hardly state-of-the-art high technology but adequate for long, slow voyages. Still, with the sails set and the engine ticking over at a moderate speed they can keep up with most cruising sailboats and, of course, outdistance them when the wind dies. And, of course, with the engine going most of the time, you have ample electric power to keep the beer cold.....



Motorsailing.
By Captain Andy Chase.
Reproduced with Cpt. Chase's permission, from his book Auxiliary Sail Vessels Operations for the Aspiring Professional Sailor (See downwards in this page)


MOTORSAILING
The majority of sailing vessels today, especially those in commercial service, are equipped with auxiliary engines. The professional skipper should know how to use the engine to maximum advantage. Too few sailors appreciate what the engine can do for them while under sail. Furthermore, the same people often do not understand that they are wasting fuel by not using their sails while motoring.

The combination of sails pulling and an engine pushing gives a result that is greater than the sum of the parts. The increase in speed produced by the engine provides an increase in the apparent wind, which allows the sails to produce greater aerodynamic lift. This not only provides more speed, but will also take some of the load off the engine, significantly improving fuel economy.

The increase in fuel economy is no small amount. In 1984 the Japanese built a small oil tanker with auxiliary sails to test the theory that sails were a valid fuel-saving device for commercial cargo ships. The designers predicted a 10 percent fuel savings over the long run. In actual practice, according to Paul Priebe in his book Modern Commercial Sailing Ship FundamentaIs, they realized fuel savings of up to 50 percent.

Since the increase in boat speed will cause the apparent wind to shift ahead, it might seem impossible to enjoy this benefit when trying to get to windward, since the sails will be luffing. This is not always the case. When motorsailing, you are not relying on the aerodynamic lift of your sails to provide the primary driving power for the vessel. They are merely giving some extra boost. You will find that you can sheet your sails in virtually flat -as flat as you can get them- and steer remarkably close to the wind. As long as the sails maintain some aerodynamic shape, they will provide some benefit. A large, gaff-rigged schooner that under sail alone could sail no closer than 55 degrees to the wind, will be able to make good about 35 degrees to the wind when motorsailing. Her speed will be commensurate with her motoring speed, or a knot or two better, and her fuel economy will be greatly improved.

Your choice of sails will be deterrnined by how close to the wind you want to run and by how flat you can trim them. Jibs may not work well, as they cannot be trimmed as close to amidships as the main, staysail, and any other boomed sails. A sloop may work best (to windward) with only the main set. If you are off the wind a bit, set anything that can be kept full.

There will be occasions when this technique will not be the right choice. If the true wind is abaft the beam, motorsailing may not make sense. The speed provided by the engine will be decreasing the apparent wind, so the technique will pay off only if there is enough wind to keep the sails full. In that case you would almost certainly be sailing instead. Also, there will be times when you will need that one mile dead to windward, in spite of the motion and the fuel cost. Then you will be taking all your sails down ( except what you might want for steadying against the roll). You certainly do not want to steam into the wind with sails luffing, as you will only add windage and damage your sails. But if you motor dead to windward for an hour, and then bear off and set some sail, you will be amazed at how much more comfortable the vessel will be with the sails drawing.

For some vessels this will not be the right choice. Square-riggers have so much rigging, and such a tremendous head rig (the entire rig forward of the bow, including the bowsprit, etc.), that they sirnply can `t be driven to windward effectively or safely in a substantial head sea, under sail or power. There is too much windage, the rig can`t take lunging into a head sea, and the head rig is too vulnerable to being driven into the face of a wave  -an action that could easily break your bowsprit or jibboom-Smaller vessels that tend to sail at substantial angles of heel may not be able to run their engines at such angles. You should be certain to check the engine manufacturer's recommendations on maximum heel before motorsailing. Some engines cannot lubricate themselves effectively if the boat is heeled past 20 or 30 degrees.

When does a sailor decide to utilize the engine? Most would say when speed under sail, either through the water or toward their goal, drops below a certain arbitrary point. Let us say you are on a large schooner, making an extended voyage of several weeks' duration, and you have laid out your schedule based on a conservative average speed of 4 knots. It would be wise to say that (at least for the first half of the voyage, until you have some miles "in the bank"), if your speed drops below 4 knots, you should start the engine. More discussion about these choices will take place in the chapter on passage planning, but for now let us work with this figure.
You are sailing close-hauled, and the wind is failing. As boat speed drops below 4 knots, the watch dutifully gives up, drops sail, and starts the engine, running at sufficient engine speed to attain 7 knots. With no sails set, they assume it makes sense to head directly toward the destination, which is dead to windward. The wind is light, blowing about 5 knots.

Steaming directly into the wind at 7 knots will produce a head wind of 12 knots, not an insignificant breeze considering the drag of all of your rigging and masts. All of this windage will hurt you in two ways. It will slow you down, and it will burn up fuel.

How much windage is there? By a conservative estimate, on an 80-foot schooner with no topmasts, a 45-foot foremast, and a 60-foot mainmast, counting masts, standing rigging, and running rigging only (not counting the hull, furled sails, and any deck gear or people), there would be about 400 square feet of "sail" area, which you will be pushing to windward. This is the equivalent of a 20 by 20  foot sail held square to the 12-knot wind.

How does this make the case for motorsailing? The wind -apparent, true, and relative- is there. You cannot avoid it, so you should use it, even when under power. In the same example as above, set your main, foresail, and fore staysail. Leave the jib down, because you cannot sheet it in as near to the centerline as the others. With these three sails set and sheeted in flat you will find that while maintaining the same engine speed you can sail to within about 35 degrees of the apparent wind, as previously explained. You will now enjoy substantially better fuel economy, probably a little more speed, and a better motion, as the thrust and inertia of the sails will dampen the vessel`s tendency to pitch and roll.

The trade-off here will be that you are no longer heading directly for your destination. To determine if the trade is a good one, a simple calculation can be performed to compare your speed made good toward your destination under power alone (heading directly toward your goal), and under the combination of power and sail while heading off a few points. Do not fail to consider the improvement in vessel motion  -and the consequent comfort to the crew- when weighing the difference.
Vessel motion when motorsailing improves more than just comfort, although saving crew energy is an important consideration on an offshore passage. A vessel pitching in a head sea is very hard on her gear. The shock loads of the masts altemately stretching their backstays, then lurching back and snapping their headstays tight, is a recipe for breakage. Likewise, when the wind and seas are more abeam, similar loads are placed on the shrouds and chainplates as the vessel rolls. With sails set and drawing, however, the loads become much more steady and consistent. Anything you can do to eliminate or reduce shock loads of this kind will greatly prolong the life of all of your gear.

The advantages of motorsailing disappear when the wind fails completely. In a flat calm, when there is not enough wind to fill the sails at all, you should strike them and proceed under power. You might choose to leave something set to help steady the vessel, but consider that that sail will take a beating by continuous luffing. A little time spent powering directly toward your goal when the sea is calm will allow you to spend more time under sail later when there is some wind.

Motorsailing.
By Bill Kimley
Reproduced with his permission. Visit Sea Horse's site, where you'll find more about Bill, at: www.SeaHorseYachts.com


I would like to share with you some thoughts about motorsailers, power-only trawler yachts, and sailboats.
Passagemaking has many areas of concern. Three of the most important ones are:
FUEL ECONOMY, both to keep costs down and provide the range needed for longer cruises,
STABILIZATION, good stabilizing is the difference between a voyage out of hell and one of the most pleasant experiences of a lifetime, and RELIABLE PROPULSION, who do you call when the engine stops.

These three concerns are addressed in a power-only vessel buy utilizing a variety of conflicting contrivances. More fuel is carried for long cruises the weight of which causes more fuel use. Extra "wing" engines are employed to back up the main engine which increases weight and hull drag causing more fuel use and are of no use in rough conditions or in case of total fuel loss. Stabilizing means dragging cables and paravanes or powered fins through the water, both of which slow down the vessel and require even more fuel. And they will not bring you to a safe harbor following total propulsion failure.

Solutions to the problems of stabilization, propulsion redundancy and fuel economy are inherent in the very concept of the motorsailer. A properly designed sailing rig stabilizes the vessel better than any mechanical device without inducing hull drag or relying on fuel dependent energy. And the rig provides total propulsion redundancy allowing the vessel to reach a safe harbor if the fuel runs out or there is a mechanical failure.

Plus the sailing rig increases the speed of the vessel so less fuel capacity is needed. This weight savings coupled with the additional propulsion power available results in faster passages and excellent fuel economy. How can this be? Well most power-only trawler yachts cruise at around 6 to 8 knots per hour depending on power, weight, hull shape and water line length. All these vessels are creating, at some expense, a wind equal to their speed. This wind, a vital and reliable source of energy, combines with and adds to the true wind to create an apparent wind across the boat which is just thrown away. The motorsailer, on the other hand, uses its rig to regain this energy resulting in increased boat speed, up to 25% above a stabilized powerboat, without increasing fuel use. At the same time the pressure of the wind impinging on the sails stabilizes the boat very well and, of course, sail only propulsion is always available if needed or desired. Life should be so good.

While Beebe's book, "Voyaging Under Power" is the bible of the power-only crowd it is interesting to note that his vessel, "Passagemaker", was a motorsailer with small a rig. Bob wanted a larger more appropriate rig but settled for the smaller rig because of the its, and a suitable folding prop's, cost. (P.20 bottom, Seven Seas edition; P.28 top, Leishman rewrite) In actual practice I feel motorsailers do not need a folding prop unless extensive sail-only passage making is planned. It is my experience that most of the time motorsailers work best in the engine running mode. Beebe's design 103 is a true 50/50 motorsailer, similar to the MANDARIN 52, which, to quote Bob, "...eliminated the faults we found in "Passagemaker". Bob called Design 103 "Passagemaker II".(P.84 2nd paragraph, Seven Seas edition; not in Leishman rewrite)

ISN'T THIS JUST A SAILBOAT WITH ITS MOTOR ON?
You may think I'm talking about a sailboat with its motor on here. Not so! A sailboat using sails and motor is, in fact, motorsailing, but it is not a "motorsailer". Some sailboat builders put a pilothouse on their sailboats and call them motorsailers. Even the newest motor sailor knows they are just trying to fool you.  A sailboat is designed to sail well on all points of sail and this means upwind. Racers can not use their motors and sailing purists love to surf up and down a multi sail inventory while sitting outside ( ! ! ) enjoying the ocean gods dumping 55 gallon drums of seawater over their heads. I've been there and did that and, at the time, even enjoyed it, sometimes. But a sailboat that's sailing well upwind carries, to varying degrees, three rather serious design compromises.
First Compromise: When a boat sails upwind part of the wind's energy is making the boat move forward, that's good; but most of the wind's energy is trying to tip the boat over, that's bad. To keep the boat from tipping way over we need ballast, like heavy heavy lead, lots of it. So this extra weight is our first compromise.

Second Compromise: Because this heavy ballast can not keep the boat from tipping over some, we need nice water planes, efficient hull bottom shapes, right up the side of the hull so that the boat can sail while heeled. This results in pinched sterns causing user unfriendly interior spaces and less form stability decreasing the effect of all that ballast.

Third Compromise: Now to make the ballast really work we need to get it low. This means deep draft usually in a fin shaped keel with an exposed rudder. Deep draft limits available cruising areas, our third compromise.

Bummer #1, you have to carry these three compromises all the time, when sailing up wind when they are needed, and when sailing on a forward reach, a beam reach, an aft reach, downwind and even at anchor, when they are not.

Bummer #2, cruising sailboats, despite carrying all these design compromises, almost never sail upwind! Cruises are carefully planned, weather systems are waited out, motors are run, all to avoid ever having to actually sail a long cruising leg upwind.

So what's different about a motorsailer? The motorsailer is a vessel that sort of sails without a motor pretty well, but not real close to the wind, and can motor along without sails OK, but may be a little stiff. A stiff hull is shaped to resist rolling. It carries sail well but it likes to float with its beam water line parallel to the water surface. A lumpy sea presents many inclined water surfaces and a stiff hull will snap around trying to parallel each one as it passes.

The designer of a motorsailer has to make the decision to exclude good upwind performance. Accepting that compromise allows a lot of neat things to happen, lighter weight, shallower draft, 5 feet is the max for most canal systems, and a more yacht trawler like hull shape with its large accommodations, especially in the aft cabin. But the neatest thing of all is the way the large motor and large sailing rig of a true motorsailer, designed with a nice slippery hull, work in harmony, the motor taking over in the lulls and the rig taking over in the puffs, to provide a surprisingly fast, fuel efficient and comfortable passage.

Note: By "Slippery" I mean a cp (prismatic coefficient) around .60 which favors the 7 to 9 knot. range.)

Comments are welcome.
Bill Kimley



Why Motorsailers?  
By Courtenay James
(Reproduced from a web Forum, with his permission)

"Any choice of boat is a compromise, but I think a motorsailer can offer a number of benefits.

THE COMPROMISED SAILING RIG... .
Some motorsailers do have a very abbreviated sail plan and are too lightly rigged for offshore sailing. I eliminate these as I would the many power boats that are unsuited to
other than protected waters. Almost all motorsailers could be said to be poor sailing performers when compared to most dedicated sailboats, but lets decide what kind of sailing performance is most important to us in this comparison. I am willing to give up light air performance and the ability to sail close to the wind (that is at an angle closer to the wind's direction). I have chosen a boat that will sail in heavier conditions safely in the knowledge that I will probably be motoring in light air, when going upwind and when in confined spaces. Good tracking ability, high ultimate stability and reasonable off wind performance is more important to me.

THE EXPENSIVE SAILING RIG...
The rig does add expense, but even with the sails furled it makes the boat much more stable than a comparable trawler without the rigging. When I was shopping for a boat last year, I decided I wanted to be able to cross the Gulf with some sense of security in less than calm conditions. From what I read on TWL, most trawler owners feel very uncomfortable about this crossing, and my experience on an unstabilized trawler makes me understand why. While rough conditions like this may not be life threatening, they certainly are much more uncomfortable on an unstabilized trawler than on my motorsailer. We crossed the Gulf from Tampa Bay to Mobile last Fall just after a hurricane. The seas weren't too large, but were very confused. We felt quite secure, and the bowl of fruit on the salon table stayed put the entire time. If one is to list the cost of the sailing rig as a negative, then the only fair comparison is to consider the cost of a stabilization system on a trawler. All the paravane and Naiad type systems I am aware of are also quite expensive and entail considerable maintenance issues as does the sailing rig.

THE CLUTTER OF THE SAILING RIG...
Another trade off is the height of the rig. I have to step my main mast on the way up the inland river system. It is a pain and unwelcome expense. Once on the rivers and lakes, the sails are not particularly useful as a means of propulsion. I choose to be somewhat limited by my mast in order to be less limited when I get to salt water. I have mast and booms and lines all about. They can be useful as lifting boom or support for a full boat awning, and at Christmas the mast becomes a 55' tall lighted tree. I don't have a large enclosed aft deck or elevated bridge. I do have a foredeck sufficiently large to accommodate me and my crew plus some guests, a seaworthy deck layout that allows for safety at sea and easy docking, and I have the added bonus of lots of winches and blocks and lines to play with. :>) I've
read on TWL of many complicated plans for "get-home-power." To each his own, but I can't consider my sailing rig any more difficult to deal with than some of the plans I've read about here.

THE MOTORSAILER IS A COMPROMISED POWER BOAT...
My boat is a full displacement hull weighing 50,000 lbs. My power plant is a single American Diesel 140hp engine. I carry 385 gal. of fuel and the same amount of water. I would NOT consider buying a trawler that planes and weighs less than half of what BLUE SHAMU does. My boat isn't BETTER because it is a full displacement hull; it is not WORSE because it can't go twice hull speed. It is simply my preference. My cruising speed is comparable to any displacement power boat with a similar engine. I have a single screw and would choose that option on any boat I bought. I have seen some displacement trawlers with more tankage (I would like that), but none with other features I wanted or in the size or price range I could afford.

MOTORSAILER ACCOMMODATIONS ARE NOT AS DESIRABLE AS THOSE IN POWER BOATS...
Interior layout is truly a matter where difference in personal taste comes to the fore. I wanted a private, comfortable, full sized bed that wasn't packed away in a claustrophobic quarter berth, nor squeezed into a narrow vee berth. I got it. I needed an extra cabin for my granddaughter who I hope will continue to enjoy the boat as much as I do. I wound up with 2 extra cabins in the bow of the boat, each with over/under bunks. I could always convert these to one enormous vee berth, but the present arrangement works for now. I don't mind having the salon and galley below decks. We have plenty of light and air from ports all around, and being lower, the movement at sea is reduced A LOT. We have a very comfortable pilothouse that is separate from living space for night passages, but large enough to lounge about in at sea or at anchor. Then there is still the cockpit and lots of deck space to enjoy. The only thing that I don't have, but would enjoy, is a permanently covered outdoor space. I may add a bimini at some point. My motorsailer has a generator, refrigeration, freezer and heat/air conditioning, and so did most of the motorsailers and trawlers I saw while I was shopping.
Motorsailers and sailboats sometimes tend to be more energy efficient than some power boats, but they aren't nearly as austere as they used to be. I have seen the accommodations in a fair number of trawlers, and IMHO the Fisher is the most comfortable boat that I have been on.

MOTORSAILERS ARE MORE EXPENSIVE THAN TRAWLERS OR REGULAR SAILBOATS...
I suppose the reasoning is that you are paying for a trawler plus a sailboat. I just don't buy it. Aside from range of price due to quality and condition, I found motorsailers to be more boat for the money when I was shopping for trawlers. Now remember, I'm eliminating a lot of the more reasonably priced trawlers (MT's for example), because I wanted a passagemaker rather than coastal cruiser. I looked at Krogens, and I liked them. I didn't see an asking price less than about $250,000 either. And boats at that price were not pristine by any stretch of the imagination. I saw lots and lots of motorsailers for far less than that. Not all were really comparable to the Krogen, but many were. And nearly all of them could cross oceans safely and comfortably. Let's face it. Trawlers are in demand now, and their prices reflect it.

CONCLUSION...
My priorities may not make sense to anyone but me. I wanted fairly specific accommodations, and I got them. I wanted seagoing capability that isn't going to be used all the time, but I want it when I need it. I was willing to give up the best sailing performance to get longer range under power. And I was willing to give up high speed to get longer range, redundant propulsion source (sails) and better fuel economy. I have a comfortable, sound boat that handles easily and looks salty. To my mind it's an enhanced trawler/sailer."

Courtenay James
BLUE SHAMU, Fisher 46 Motorsailer, Chattanooga, TN